JavaScript can detect and respond to browser and platform features and limitations -- but the rise of mobile/tablet devices has meant that irreconcilable differences in browser and display capabilities run deep enough for a standard, not an application, to handle them.

CSS3 media queries, which detect and respond to browser properties, address these differences immediately. They aren't the only CSS3 feature that should prove useful to responsive web designers, though.

Katrien De Graeve points out that at least three features are necessary for good responsive web design: